1. Field of the Invention
The present invention relates to a motor control device for driving a motor (particularly, a brushless motor). The brushless motor is utilized as a generation source of steering assist force in an electric power steering apparatus, for example.
2. Description of Related Art
A motor control device for a brushless motor is provided with: a current detection portion; a rotational position detection portion; a dq-axis target-current calculation portion; a dq-axis current calculation portion; a d-axis voltage command value calculation portion; and a q-axis voltage command value calculation portion. The current detection portion detects a current flowing through an armature winding of a motor. The rotational position detection portion detects a rotor rotational position of the motor. The dq-axis target-current calculation portion calculates a d-axis target current and a q-axis target current. The dq-axis current calculation portion evaluates a d-axis current and a q-axis current based on the detected armature winding current and rotor rotational position. The d-axis voltage command value calculation portion evaluates a d-axis voltage command value based on a PI calculation of a d-axis deviation so that the d-axis deviation between the d-axis target current and the d-axis current is decreased. The q-axis voltage command value calculation portion evaluates a q-axis voltage command value based on a PI calculation of the q-axis deviation so that the q-axis deviation between the q-axis target current and the q-axis current is decreased. Based on the d-axis voltage command value thus evaluated, the q-axis voltage command value thus evaluated and the detected rotor rotational position, the motor control device applies voltage to the armature winding. Thereby, the rotation force of the rotor is generated.
On the other hand, there is known a non-interacting control in which a non-interacting control amount is added to a PI calculation value (see US 2001/0005121A1). The non-interacting control is a control which defines a voltage command value so that compensation is made for a speed electromotive force generated inside a motor along with the rotation of the rotor. It is expected that when the non-interacting control is performed, a decrease in responsiveness and tracking resulting from the speed electromotive force can be effectively inhibited.